Vascular catheters are typically connected to external fluid sources via hubs with, for example, luer connections. When a luer tip is removed from a catheter, a pressure differential is created which sometimes causes blood to reflux into the catheter where it can clot, occluding the catheter or becoming a nidus for infection. In practice, this pressure differential is addressed by the use of external manual clamps—which must be closed by an operator when a connection is withdrawn—or through the use of internal catheter valves, which mechanically isolate the lumen of the catheter from changes in pressure at the hub with limited operator input. Internal valves have the benefit of operating rapidly and reliably to prevent transmission of negative pressure without the risk of operator error.
State of the art valves for vascular applications, such as the PASV® Valve produced by Navilyst Medical, Inc. (Marlborough, Mass.), typically comprise an elastomeric disk that includes one or more slits along an axis of the disk. If the disk is not round (e.g. if it is elliptical), the slit is typically oriented along the major axis of the disk. When a fluid pressure differential of sufficient magnitude arises across the disk, the disk deforms so that the edges of the slit or slits are separated and fluid can flow across the valve. The pressure necessary to deform the disk depends on variables which may include, without limitation, the thickness of the disk and the Young's modulus of the material used.
Although the disk may be able to deform very rapidly, some latency may inevitably exist between a change in the pressure across the valve and the time that flow across the valve reaches a steady state. It is preferable to minimize the response time of the disk in order to minimize the potential for reflux. Additionally, when the pressure differential across the valve drops below the threshold magnitude and the valve returns to its relaxed state, it should seal completely to avoid leakage through the valve. There is a constant need to improve valve durability and minimize the risk of leakage.
The needs described above are magnified in high-flow or “power injection” applications, such as infusions of contrast agent for contrast-enhanced CT scanning. All valves are subjected to pressure and resist flow to some degree, but valves used for high flow applications are larger and have greater surface areas, and are thereby subjected to greater pressures than other valves, making the issues described above particularly acute. Additionally, valves that are configured for low pressure uses may fail when exposed to the high flows and pressures required for contrast agent infusions. There is a constant need for valves suitable for power injection with improved response and sealing characteristics.